I have a 2018 SGS. I had my first oil change done at the dealer and im pretty sure my oil was low but I didnt know where I started so I didnt care to much about that one..
Now, everyone who looks into this knows HD says 1 quart per 1500 miles is acceptable loss for the M8 engine.
After my 1k service I verified where everything was/is and continued to check it at least weekly (Hot, on the stand, and after a ride). I am right at 4k miles right now. All looks good, but I have lost Two Pairs of dots on the stick. So if you look at the dipstick and it says "hot on the jiffy stand" I had my bike filled purposely halfway up the dot matrix ( I believe there are 10 sets of dots).. Just in the last 500 miles or so I have started to see loss. I have now lost as of tonight two/maybe 3 dots.
Not sure what that equates to in Ounces, pints, quarts, etc. but im sure its not much at all to worry about.